It is still better than in currently existing centralized solutions when casino can disappear just like that and get the funds from the player. It is of course possible to replace 2-of-2 multisig with some kind of 2-0f-3 multisig, but then a lot of trust is put into some escrow service that may or may not be honest. By freezing the funds, both players are incentivized to remain honest, as they both lose if they stop cooperating: the winner will lose the coins, but will have the proof that somebody was dishonest, so the loser will lose some reputation. And everyone else's coins will be worth more, because these coins will be thrown out of circulation.